Mesitylene manufacture



A. P. LIEN ErAL MESITYLENE MANUFACTURE March 18, 1952 2 sl-xEET's-SHEET 1 Filed Dec. 15, 1948 A7' TOR/VE Y March 18, 1952 A. P. LIEN ETAL MESITYLNE MANUFACTURE 2 SHEETS-SHEET 2 Filed Dec. 15, 1948 vsupported by alumina or magnesia.

Patented Mar. 18, 1952 MESITYLENE MANUFACTURE Arthur P. Lien, Hammond, Ind., and David A. McCaulay, Chicago, Ill., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application December 15, 1948, Serial No. 65,496

Claims.

, v 1 This .invention relates to a process for the treatment of trimethylbenzenes with liquid I-lF and 13113,Y In one aspect, this invention is concernedwith a process for the isomerizationv of trimethylbenzenes, particularly the isomerization of trimethylbenzenes isomeric With mesitylene to produce mesitylene.

One' object of this invention is to provide a process for the selective extraction of mesitylene from its'- mixtures with isomeric trimethylbenzenes. Another object is to provide a process for the high temperature conversion of trimethylbenzenes in the presence of liquid HF and BFS Still another object is to provide an efcient process forV the manufacture of mesitylene by the isomerization of pseudocumene and hemimellitene or hydrocarbon fractions containing the same in the presence of liquid HF and BFs.' Yet another object of our invention is to provide a novel process for the treatment and separation of the products produced by the high temperature treatment of trimethylbenzenes with liquid HF and BFa. v Probably the most important source of trimethylbenzenes or of hydrocarbon fractions containing substantial proportions of trimethylbenzenes is the catalytic hydroforming process. In this process a petroleum naphtha, which may be aivirgin or cracked naphtha or a mixture of both, isconverted to aromatic hydrocarbons by contact'- with a solid, porous dehydrogenation catalyst at a temperature in the range of about 850.:F.- to about 1050 F., preferably `in the presence of hydrogen. Suitable catalysts are oxides. of metals of groups 2 to 6 of the periodic system,rparticularly oxides of 6th group metals such-a's chromium and molybdenum, preferably Excellent catalysts can be prepared by depositing about 4 to about 10% of molybdenum oxide upon an activated alumina. Suitable space velocities for hydroforming fall within the range of about 0.2

- to about 4 volumes of the liquid charge per hour f 25, 1946), pp. 611-637.) 'Triniethylbenzenes are found in considerable concentration in hydrocarbon fractions pro- 4 duced by' catalytic .hydroforming' boiling within the'range of about 160 to about 180' C. 'Concentrates of pseudocumene and hemimellitene version of trimethylbenzenes are found in hydroformate fractions boiling between about 167 and about 180 C.

While the catalytic hydroforming process is probably the most important source of trimethylbenzene-containing hydrocarbon fractions at the present time, it is not the exclusive source thereof. Thus, hydrocarbon fractions containing trimethylbenzenes can be obtained by fractionation of coal tar naphthas and kerosenes. Also the presence of various trimethylbenzenes has been noted in virgin petroleum naphthas and kerosenes, and trimethylbenzenes fractions can be obtained therefrom by selective solvent extraction and precise fractional distillation. Likewise, selective solvent extraction and fractional distillation of cycle stocks from the cracking of heavy oils with solid cracking catalysts such as silica alumina or silica-magnesia, yield hydrocarbon fractions containing trimethylbenzenes. The high temperature processes for producing trimethylbenzenes such as coking of coal or. high temperature cracking of oils yield hydrocarbon fractions containing the trimethylbenzenes in proportions conforming substantially to the thermodynamic equilibrium. The principal component in trimethylbenzene mixtures produced by high temperature processes is pseudocumene which occurs together with relatively smaller proportions of hemimellitene and mesitylene (Wm. J. Taylor et al., J. Res. Nat. Bur. Stds. 37, 117 (Figure 5) (August 1946)).

The process of the present invention provides a means for effecting the substantial conisomeric with mesitylene to mesitylene. Of all the hydrocarbons tested thus far; mesitylene has the highest blending octane number and is among the highest in clear CFR-R octane number. A comparison of the octane number of mesitylene-with other aromatic hydrocarbons is shown in the following table:

CFR-R Octane Numbers p-Xylene Comparative antiknock ratings of theindividual isomeric trimethylbenzenes in a 3C engine showed hemimellitene to have a very similar performance to pseudocumene and both to be very much inferior to mesitylene.

Mesitylene is isomeric with cumene which is extensively used as a high octane number aviation gasoline component, has similar physical properties, e. g. volatility characteristics,I and would thus be a valuabe constituent of safety ,v fuels. Mesitylene has not heretofore been avail-v able in concentrated or pure form in commercial quantities at a price consistent with the prices of other aromatic hydrocarbons. The

process of the present invention yields mesity-v lene as a relatively low cost aromatic hydrocarbon concentrate and the process is suitable for large commercial installations. The mesitylene: concentrates produced by the present process may be employed in various chemical conversion operations, for example, oxidation in much the same manner as naphthalene or xylenes to pro- :duce the corresponding` 1,3,5,benzenetricarboxylic acid, which is suitable for the production of alkyd' type resins and plastics. Numerous other'uses for mesitylene or mesitylene concenltrates produced by the process of the present invvention will no doubt suggest themselves to those 'skilled in the art.

' lWe have found that mesitylene dissolves in liquid HF containing BFQ` and that the solution process is attended by a formation of a strong complex of mesitylene with HF-BF3, said complex containing 1 mol each of HF, BF: and

mesitylene. The trlmethylbenzenes isomeric with mesitylene also dissolve to some extent in 'liquid HF containing BF: but the complexes formed between these trimethylbenzenes, HF and BFa appear to be much less stable than the mesitylene-HF-BFs complex. At the relatively'high temperatures used in the conversion process of the present invention it appears that the complex of mesitylene with HF and BFS can exist under the conversion conditions whereas it appears quite certain that the complexes of pseudocumene and hemimellitene with HF and# v1MB-F3 are decomposed to a very substantial degree under the conversion conditions. The equi- "librium in the conversion process of the present invention is, therefore, displaced very largely 'towards the production of mesitylene and is far diiferent from the thermodynamic equilibrium. It should be understood that we do not choose tobe bound by any theory concerning the procemploy between about and about 200 volume 'percent HF based on trimethylbenzenes charged, although much larger amounts of HF, up to about 1,000 volume percent or even more, based on the trimethylbenzenes charged, may be employed. We prefer to employ amounts of HF varying 'between about 60 and-about 120 volume percent,

based on the hydrocarbon charging stock. Conversion .is generally` effected at temperatures between about 150 F. and about 400 F. and,

in general, we prefer to employ temperatures between about 170 F. and about 250 F. The conversion is effected at a pressure suiiicient to maintain a liquid phase in the reaction zone; it should be understood, however, that a substantial partial pressure of BFS may exist in the gas phase in the reaction zone, for example, between about 50 and about 400 p. s. i. g.

We have found that the equilibrium distribution of trimethylbenzene isomers in the conversion products is dependent upon the BF3 trimethylbenzene mol ratio. At BFa trimethylbenzene mol ratios substantially below l, for example 0.1,v the ordinary thermodynamic equilibrium is achieved (about 60 percent pseudocumene, 10 percent hemimellitene and 30 percent mesitylene). However, at BFS trimethylbenzene mol ratios near 1, the mesitylene concentration in the C9 conversion products approaches 100 percent. Therefore, in the conversion process of this invention we employ BFg in amounts sufiicient to produce Ya BFS trimethylbenzeneA mol ratio of at least about 0.75, for example between about 0.75 and 1.25, although we may employ even higher ratios, such as 2 or more. 'Boron trifluoride, however, is a relatively expensive chemical and ordinarily it will be desired to use the minimum amount necessary toachieve the desired results. Also, as the BF2. trimethylbenzene tmolar ratio) increasesabove 1,' the operating pressure in the reaction zoney increases tremendously because of the high vapor pressure of the free BFa.

In the following tabulation of examples, m-xylene was disproportionated by treatment with liquid hydrogen fluoride and Bl to produce mesitylene and the effect of 'the BFa trimethylbenzenes mol ratio on the equilibrium C9 product distribution` was noted, In Example l the minimum calculated BFa trimethylbenzenes mol ratio was 1.3, assuming percent disproporticnation of the xylene charging stock. Since only about half the xylene was converted it will be apparent that the actual mol ratio of BFs trimethylbenzenes was somewhat greater than 2. It will be noted that in Example 1 the sole surviving trimethylbenzene was mesitylene. In Example 2 Where the mol ratio of BF3 trimethylbenzenes was substantially below 1 it, will be noted that the concentration of mesitylene in the CQ reaction products was reduced to 60 percent.

Examples 3 and 4 were studies of the trimethylbenzenes isomerization equilibrium in thev presence of liquid HF and BFa. Example 3 indicates that the isomerization equilibrium was not attained at 212 F. with a small amount of BFa, although a considerable amount of disproportionation occurred even under these relatively mild conditions. in Example 4 it was found that the addition of toluene suppressed the dis- Y percent mesitylene in the C9 conversion products l by .using a. suicient amount of' BFa Vin the re- .'action zone to' provide a. BFs trimethylbenzen'es mol ratio of about 1 or more.

iinic hydrocarbons. liquid hydrogen iuoride (280 g.) and BF3 (122 g.)

ISQIERIZATION 0F PSEUDOCUMENE The pesudocumene employed was obtained by precise fractional distillation of a sample of Eastman-Kodak Company trimethylbenzenes in a -fractionating column containing the equivalent of 100 theoretical plates. The fraction boiling at 167l71 C. was taken as pseudocumene. This fraction contained 90 percent of pseudocurnene, the main impurities being close-boiling paraf- Pseudocumene `(215.5 g.),

werecharged to a stirring autoclave and agitated at 180 F.`for 30 minutes. The contents of the autoclave were then withdrawn into 400 cc. of

water and the resultant hydrocarbon -layer wasv separated from the aqueous layer. The recovery of hydrocarbons was 92.6 weight percent of the .hydrocarbons charged. 'I'he hydrocarbon product was fractionated in a fractionating column containing the equivalent of theoretical plates with the results shown in Figure 1.

The composition of the C9 product fraction 'shows that mesitylene was substantially the sole isomerization product of pseudocumene. This demonstrates that the thermodynamic C9 iso- .l

merio equilibrium distribution, in ,which the pseudocumene-mesitylene ratio is about to 40, canv be shifted by one mol of BF: per mol of feed stock to give a product containing practically 100% mesitylene in the Ca fraction.

Some'disproportionation of vpseudocumene also occurred, as shown in thetablebelow; giving the following overall product distribution:

Composition of pseudocumene isomcte, mol

The ethylxylene may have been formed from an ethyltoluene impurity inthe feed or may have resulted from cracked parafns alkylating an aromatic. Y'

I The composition of the Cio product fraction boiling at 198 C. is remarkable in that it consists TABLE 1 Example l 2 3 4 Feed m-xylene m xylene.: mesitylene mesitylene grams. 259 261i` 345 122 HF, weight (g). 30o 300 40o 243 BFQ, weight (g 109 13. 20 8 mols 1. 6 0. 19; 0. 295 0.118

Temperature,A 212 250 212 250 Mols BFg/Cej, (Assuming Conv. of Xylene 1. 3 0.16 0, l 0.12 Reaction time, min 30 30 30 30 Product Distribution, Vol.

lPer Cent: 3*,

Toluene 17 1 3 1 32 Xylenes 57. 5 GZ 8 22 Trimethylbenzenes 25. 5 77 46 Cw and higher aromatics 1 14 Compositionflrimethylbenzene,

Vol. Per Cent: I

1,3,5-Trirnethylbenzene 100 60 -10 1,2,4-Triinethylbenzeue Trace 40 2 60 1,2,3-Trimethylbenzene do Trece Trace Trace l Mixture. 'l yDur-ene is the predominant isomer. 2 rlfoluene, 84 g.

Eample 5 05 of only one isomer, namely isodurene. In Example 3, in which mesitylene was isomerized and disproportionated in the presence of small amounts of BFS, the C10 product fraction was a mixture of which the predominant isomer was durene. Thus it hasz been shown, among the tetramethylbenzenes as Well as the trimethylbenzenes, that the ordinary thermodynamic isomeric equilibrium distribution can be shifted toward the formation of one isomer. Therefore, one of the lay-products of the isomerization of pseudocumene, in the presence of,an equimolar amount of BFa', is a substantially pure isodurene which should be of great value as a pure chemical.

In cases where it is desired to suppress the disproportionation reaction, we have shown in Example 4 that this can be done by adding toluene to the reaction mixture. Thus, the net disproportionation of trimethylbenzenes in Example 4 at the relatively elevated temperature of 250 F. was less than that obtained at 180 F. in the absence of toluene. Xylenes or a mixture of toluene and xylenes maybe used in lieu of toluene. Another possibility is the use of a lower temperature, about at which rate of disproportionation relative to isomerization may be decreased considerably.

In order further to illustrate the conversion process of the present invention, reference is made to Figure 2. `A trimethylbenzenes fraction, suitably a hydroformate fraction boiling between about 160 and about 180 C., preferably about 167 to C., may be charged through line I0 into the lower portion of an extraction tower I I, provided with suitablevpacking material I2, e. g. shaped fragments of; carbon, Monel metal and the like, and a cooling coil I3 to remove the heat vvvof absorption. Liquid hydrogen fluoride is in- 'troduced into tower II through valved line I4. BFs may be introduced into' tower-II through valved lines I5 and Iliand/or through valved line vI6 and manifold I1.

The conditions of extraction may be adjusted to dissolve substantially all the aromatic hydrocarbons contained in the charge entering tower I I through line I0. For this purpose the feed stock is contacted with liquid hydrogen fluoride in an amount between about 0.75 and about 7.5 volumes per volume of trimethylbenzenes contained in the feed stock and with BF's in an amountvat least equimolar with the aromatic hydrocarbons contained in the feed stock, for

example, between about 1 and about 3 mols of BFa per mol of aromatic hydrocarbons. Extraction of aromatic hydrocarbons from nonaromatic hydrocarbons in the feed stock to tower I I can be effected at temperatures between about F. and about 150 F., preferably at temperatures between about 60 F., and about 100 F. The extraction period may vary between about l and about 30 minutes and usually falls in the range of about 5 to about 15 minutes. Sucient pressure is maintained in the extraction zoney to provide liquid phase operating conditions. As a result of the extraction operation a rafnate layer of undissolved, predominantly saturated hydrocarbons forms as an upper liquid layer in the extraction zone and is separated by a meniscus I8 from the extract layer of aromatic hydrocarbons dissolved in liquid HF and BFa which is present in the lower end of tower II. The raffinate is discharged from tower II through valved lines I9 and 20 and the extract solution is discharged through valved line 2|.

As has been indicated above, mesitylene is more readily converted into a complex with liquid HF and BFa-and the resulting complex is more stable than the complexes of pseudocumene and hemimellitene withHF and BFa. Therefore, byrem- .ploying a mol ratio of BFs mesitylene in tower I I. between about 0.5 and about 1.5, preferably-between about 0.8 and about 1.2, depending onA the mesitylene content, it is possible to eiect substantial selective dissolution of mesitylene from the Afeed stock in preference to pseudocumene'and hemimellitene. The mol ratio of BFa to rnesii ylene ideally should be about 1. The mol ratio of BFs to trimethylbenzenes can be varied between about 0.2 and about 0.8, depending on the mol fraction of mesitylene in the trimethylbenzenes. vIn that case the extract layer leaving tower II through lineV 2l is a mesitylene concentrate in liquid HF and BF3 and the ramnate phase leaving tower II through valved line I9 contains considerable amounts of pseudocumene and hemimellitene in addition to saturated hydrocarbons. As will be pointed out in detail hereinafter, the raffinate layer from tower I I containing pseudocumene and hemimellitene may be employed as the :charging stock to the catalytic conversion operation. A

Usually, the C9 aromatic hydrocarbon fractions derived from hydroforming, Vc'o'al tar distillation, n

and the like contain considerable 'proportions of ethyltoluenes in addition to trimethylbenzenes. We have observed that an ethyl group attached to an aromatic nucleus disproportionates Vvery readiiy in the presence of liquid hydrogen fluoride and BF3. Thus, we have noted that ethyl group disproportionation from an aromatic nucleus in thev presence of liquid HF and BF proceeds substantially quantitatively at temperatures aslow as .6 C. When ethyltoluenes are 'contained in the feed stock to tower I i considervable ethyl group disproportionation may occur to produce toluene and C11 aromatic hydrocarbons. At ordinary temperatures, we have observed that toluene forms no complex with liquid HF and and is therefore substantially insoluble in these reagents. Toluene will therefore be rejected withV the raiiinate leaving tower IlY through line The C171 aromatic hydrocarbons produced oy dlsproportionation of ethyltoluenes willv comprise diethyl-toluenes and ethyl-trimethylbenlzenes which will disso'lve to a substantial extent the liquid hydrogen fiuoridev and BF3 in towei` Y' i l. A

-tion or conversion operation in that case will -be the raiinate passing overhead from tower II through valved line 3|, thence to line 29 leading to reactor .66. However, the extraction of mesitylene from other trimethylbenzenes is ordi- 1- narily not 100 percent selective. By heating the liquid contents in drum 2 5 by means of A,heating coil 28, BFs maybe flashed off through valved line 2 .in an amount suicient vto reduce its concentration in the liquid phase to a value between about 0.2 and about 0.9 mol per mol of contained aromatic hydrocarbons, preferably about 0.6 to about 0.75 mol per mol of contained aromatic hydrocarbons; upon cooling to a temperature between about 0 F. and about 150 F., e. g. the liquid contents separate into two immis'cible phases, the upper phase flowing over Weir 26 into the upper end of the drum. The upper liquid phase in drum 25`comprises a substantial proportion of pseudocumene and hemimellitene which may be discharged through valved line 25J-to pass to the conversion zone as will be described hereinafter. The solution in the lower end of drum`25 comprises mesitylene, relatively small amounts of mesitylene isomers and in some cases diethyltoluenes and ethyltrimethylbenzenes dissolved in liquid HF and BFa. This solution may be removed from the lower end of drum 25 through valved line 3B for treatment to remove HF and BFs and for fractionation as will be described hereinafter.

When the extraction conditions in tower l I are adjusted to dissolve substantially all the aromatic hydrocarbons in the feed stock in the liquid HF-BFa and to leave only saturated hydrocarbons as the raflinate, it may be desired to pass the entire extract phase through line 2i and valved line 22V into line 29Vand thence to reactor 56 for conversion. A desirable alternativei's to pass the extract; solution into drum 25 and to vaporize BF3 therefrom to reduce the concentration of BFs in the liquid contents of drum l25 to a value substantially below l mol per Amol of aromatic hydrocarbons therein contained, for example to a value between about 0.8 and about 1.2 mols of BFa, say 1.0 mol of BFS, per mol of contained mesitylene. As a result of BFs removal in drum 2,5, the homogeneous liquid solution therein separates into two distinct liquid phases, viz. a hydrocarbon phase comprising pseudocumene and hemimellitene which collects in the upper portion of drum 25 and may be withdrawn through valved line 29 for conversion in reactor BS as hereinafter described, and a lower phase which is a solution of hydrocarbons comprising mesitylene in liquid hydrogen fluoride and BFa.

The solution of mesitylene and other hydrocarbons in liquid hydrogen fluoride and BFa which is'withdrawn from the lower end of drum 25 through valved line 30 is passed through a heat exchanger 32 into the upper portion of a stripping tower 33 provided with a heating coil 3e in the lower portion thereof. The operating conditions in tower 33 are adjusted to vaporize substantially all the` HF andi-BF: contained, in the solution charged to the tower; suitable operating conditions in tower 33 are a top temperatureVv between about 150"y F. and about 250 F., a bottom temperature betweenabout 250 F. and about 450 F. and pressures between about and about 100 p. s. i. gv. The HF and BFs passing overhead from tower 33 through valved line 35 may suitably bey .condensed and recovered for use in the extraction process in tower, Il and/or for reaction in the reactor 66. 'Ihe stripped hydrocarbons pas'sfrom the bottomof tower 33 through line 36 andheatexchanger. 31 into a fractionating tower 38 provided withreboiler coil 39. Xylen'es initially present in the feed or formed as byproductsfin the. operation in tower ll are vaporized' and pass overhead'through valved line 40 into fa condenser 4I., thence to an accumulator drum 42 'Whence a portion is recycled through valved line 43 as reux foil tower 38 and the net Xylenes production may be withdrawn through valved line 44. If desired all or part of the xylenes may bewithdrawn through line 45 to pass rto line 29, thence to reactor 66 in order to minimize the disproportionation of trimethylbenzenes Ato form C aromatics and higher boiling products. Tolueneand/or Xylenes (from any source) may be introduced into reactor 66 in amounts between about 10 and about 80 volume percent, preferably between about and about 50 volume percent based on the trimethylbenzenes charged to the reactor.

Bottoms are withdrawn from tower 38 through valved line 46 whence they pass through heat exchanger 41 into a fractionating tower 48 provided with a reboiler coil 49. The operating conditions in tower 49 are adjusted to cause the fractional distillation of trimethylbenzenes and to produce av liquid bottomsfraction comprising C10, Q11 and higher molecular weight aromatic hydrocarbons. Suitable operating conditions are an overhead temperature between about 325 and about 330 F. andbottom temperaturebetween about 355 and about 365" F.vat aboutl atm. A bottoms fraction' comprising; Cio and'higher aro'- niati'c `hydrocarbons is withdrawn from tower 48 through valved line 50. A trimethylbenzenes vaporfraction comprising principally mesitylene passes overhead from tower 4,8 through valved line '.51' andcondenser 52 into an accumulator drum, Ywhence va portion is recycled through v alvdfline 54 to reflux tower 48 and the net trinietliylbenzenes distillate (a mesitylene concentrategcan be removed as product through valyedlineA; alternatively the distillate may be .passed from linei into valved line 55B, thence. into a supeifractionating tower 56.

`,."I'nay be" vwithdrawn from valved line 55A through valved line 62, thence through valved line 63 and line 24 to serve as a backwash in drum 2'5'and/or through valved line 64 to serve as a l0 fractionating tower 56 through valved line 65 for passage to reactor 66.

Also, the charging stock to reactor 66 may be a crude C9 aromatic fraction fromhydroforming or a trimethylbenzenes fraction from any other sour-ce and may be charged to reactor 66 through valved line 61. Other charging stocks for reactor 66 may be a concentrate of. trimethylbenzeries isomeric with mesitylene derivedvfrom the ex-l traction tower Il and passing from line 3| into line 29 and/or derived lfrom the upper hydrocarbon phase in drumA 26,V prepared by the 4method-s described in detail above. f

The conversion oftrimethylbenzenes in accordance with our process to produce a C9 aromatic product fraction comprising principally mesity#A lene, usuallyebetween about and 100 percent mesitylene, is effected by agitating the hydro# carbon charging stock in reactor 66 by means of an agitator 68 or an equivalent device at a temperature between about D F. and about 400"1F.,` suitable temperature control being maintained in' reactor 66 by a heating jacket 69. Liquid HF may be introduced into reactor 66 as -needed through valved line 10 and BF3 may be intro'- duced through valved line 1I. The hydrocarbon charging stock in reactor 66 is intimately contacted with between about 40 and about 200 volume percent of liquid hydrogen fluoride and with at least about 1 mol of BFa per mol of tri-- methylbenzenes in the feed. At highertemperatures within the reaction temperature range, for example temperatures of about F. or more and with BF3:t1-imethylbenzenes mol ratios .or 1 or more, more or less disproportionation may occur as a side reaction in the isomerization of times may vary between about 3 and' about 60 minutes.

Upon completion of the desired reaction in reactor 66 the reaction mixture is withdrawn lthrough valved line 'l2 into cooler 13, whence all or a portion may be passed through valved line "I4 into line 24 and drum 25 and all or the remainder may be passed through valved line l5 into line 30',

If 1,1.: desired, `a portion of the'net mesitylene produc-- tio tion'A ofl mesitylene isomers,- viz., pseudocumene recycled through valved line 60 as reux to tower 56 and the net mesitylene production maybe vwithdrawn tljirougb4 lvalved line 6I. Trimethylb enzenes islomeric with mesitylene arewithdrawn asa. litem-129i ses :faction .dem @heavier-empf .as hereinbeioreA described, viz., an upper hydrocarbon phase comprising a substantial proportion of mesitylene isomers, which .are -recycled to.

" reactor 66 through valved line 29 and a solution comprising mesitylene in liquid HF and' BFa which is withdrawn from drum 25 to valved line 30 and `passed into the fractionation system as hereinbefore described.

Although Figure 2 describes Ya ycontinuous ex- 'traction operation, the process of our invention: 'as Example 5 clearly shows, can be operated batchwise.

Suiucient pressure is main-v asaoa 1 11 solvent extraction processes and in processes wherein liquid catalysts are, contacted with hydrocarbons may be employed to practice the process of our invention.

Although HF and especially BF3 are relatively expensive reagents and would of necessity be recovered in any large commercial application of the process of this invention, in small scale operations the recovery of these reagents might be considered immaterial. When the recovery of HF and BFS as such is not required, the distillation and stripping operations illustrated in Figure 2 may be dispensed with. As an alternative to distillation of the extract phase (or of the reaction mixture derived from reactor 66), said phase may be mixed with water, alkaline or acid solutions, or the like which dissolve" the HF and BFz, leaving a supernatant hydrocarbon phase which may then be recovered. A desirable acidic solution with which to treat the extract phase is the azeotropic HF-HzO solution, which becomes enriched in HF upon contact with the extract phase and from which the HF in excess of the azeotropic amount can thereafter be readily re covered by distillation. An alternative would be to distill free HF and BFs from the extract phase, following which the residual firmly bound BFs-HF-mesitylene complex could be treated with water or aqueous alkaline or acidic solutions to liberate the mesitylene bound in said complex. In place of the aqueous solutions mentioned above, one may employ organic compounds capable of forming complexes with HF and BFz and which are capable of displacing mesitylene from its complex with HF and BFs, e. g., organic compounds having a more basic (greater electrondonating) capacity than mesitylene. Such organic compounds include various amines, sulfur compounds, e. g., alkyl bisthioethers, and oxygenated organic compounds such as phenol, alkyl ethers, ketones, aldehydes, etc.

This application is a continuation-in-part of our application for Letters Patent, Serial No. 46,135, filed August 25, 1948, now U. S. Patent 2,564,073 issued August 14, 1951.

Having thus described our invention, what we claim is:

1. In a process for the preparation of mesit ylene by liquid-phase isomerization of a trimethylbenzene isomeric therewith in the presence of liquid hydrogen fluoride and BFa, the improvement which comprises effecting said isomerization at a temperature between about 150 F. and about 400 F. in the presence of at least about 15 percent by volume of liquid hydrogen fluoride and at least about 0.75 mol of BFS per mol of said trimethylbenzene, whereby a reaction product is produced containing mesitylene in a proportion greater than the equilibrium proportion thereof in the absence of BFs and in a proportion equivalent to at least about "I5 percent of the trimethylbenzenes contained in said reaction product, and thereafter separating mesitylene from said reaction product.

2. The process of cla-im l wherein said trirnethylbenzene isomcric with mesitylenev is pseudocumene. n `3. The process of "claim l wherein said isomf erization is eifected in the presence of between about l0 and about 80 volume percent of toluene, based on said trimethylbenzene isemeric with mesitylene.

Y .4. The process of claim 1 wheren said isomer ization is effected in the presence of between about and about 80 volume percent of xylenes", I

12 based on said trimethylbenzene isomericl with mesitylene.

5. In a process for the preparation of mesitylene by liquid-phase isomerization of a trimethylbenzene isomeric therewith in the presence of liquid hydrogen fluoride and BFa, the improvement which comprises effecting said isomeriza` tion at a temperature between about 150 F. and about 400 F. in the presence of between about 15 and 200 percent by volume of liquid hydrogen fluoride and between about 0.75 and 2 mols of BFS per mol of said trimethylbenzene, whereby a reaction product is produced containing mesitylene in a proportion greater than the equilibrium proportion thereof in the absence of BF: and in a proportion equivalent to at least about 'l5 percent of the trimethylbenzenes contained in said reaction product, and thereafter separating mesitylene from said reaction product.

6. In a process for the preparation of mesitylene by liquid-phase isomerization of a trimethylbenzene isomeric therewith in the presence of liquid hydrogen fluoride and BFs, the improvement which comprises eiecting said isomerization at a temperature between about 150 F. and about 180 F. in the presence of at least about 15 percent by volumeof liquid hydrogen fluoride and at least about 0.75 mol of BF: per mol of said trimethylbenzene, whereby a reaction product is produced containing mesitylene in a proportion greater than the equilibrium proportion thereof in the absence of BF3 and in a proportion equivalent to at least about percent of the trimethylbenzenes contained in said reaction product, and thereafter separating mesitylene from said reaction product.

7. A process for the isomerization of a trimethylbenzene isomeric with mesitylene, which process comprises contacting said trimethylbenzene in an isomerization reaction zone with between about 15 and about 1,000 volume percent of liquid hydrogen fluoride and between about 0.75 and about 2 mols of BFs per mol of said trimethylbenzene at a temperature between about.

BF3 and mesitylene and a predominantly hydrocarbon stratum comprising a trimethylbenzene isomeric with mesitylene, and separating mesitylene from said solution.

8. A process for the isomerization of a trimethylbenzene isomeric with mesitylene, which process comprises contacting said trimethylbenzene with between about 60 and about 120 volume per cent of liquid hydrogen fluoride and with BFa in an amount sufficient to aiord a parrtial pressure of BFa between about 50 and about 400 p. s. i. g. at an isomerization reaction teme perature in excess of about F. but not in`eX- cess of about F. under a pressure suicient at least to maintain a liquid phase andrfor a period of time suilicient to effect substantial isomerization, and thereafter separating. a C9 isomate containing at least about 75% of mesitylene from the resultant reaction products.

9. A process for the isomerization of a trirneth- 13 ylbenzene isomeric with mesitylene, which process comprises contacting said trimethylbenzene in an isomerization reaction zone with between about 15 and about 1,000 volume percent of liquid hydrogen uoride and between about 0.75 and about 2 mols of BFs per mol of said trimethylbenzene at a temperature between about 150 F. and about 400 F. under pressure suicient to maintain the liquid phase and for a period of time sufficient to effect substantial isomerization, thereafter withdrawing at least a portion of the reaction mixture from said isomerization reaction zone, withdrawing BFa from said mixture in an amount suficient to reduce the BFs concentration in said 4mesitylene with liquid hydrogen iluoride in an amount between about 0.75 and about 7.5 volumes per volume of said trimethylbenzene and with BFa in an amount between 0.2 and about 0.8 mol permol of total trimethylbenzenes and about 1 mol per mol of mesitylene contained in said hydrocarbon fraction at a temperature between about 0 \F. and about 150 F. under a pressure suflicient to :maintain the liquid phase, separating the resultant mixture into a rst liquid layer consisting essentially of hydrocarbons comprising tolueneiproduced by the disproportonation of said ethyltoluene and comprising a trimethylbenzene isomeric with mesitylene, and a second immiscible liquid layer which is a solution comprising HF, BFs and mesitylene, separating said liquid layers, contacting said first liquid layer with liquid hydrogen fluoride in an amount between about and about 200 volume percent, based on the voldine of trimethylbenzene contained in said rst liquid layer, and with BFs in an amount between about 0.75 and about 1.25 mols per mol of trimethylbenzene contained in said rst liquid layer at a temperature between about 150 F. and about F. under a pressure suflicient to maintain the liquid phase and for a period of time suicient toleffect substantial isomerization, and thereafter separating mesitylene from the resultant reaction products.

ARTHUR P. LIEN. DAVID A. MCCAULAY.

REFERENCES CITED Name Date Passinoet al Aug. 12, 1947 Number 

